Traditional geodesic domes and structures are based on the pioneering work of R. Buckminster Fuller described in his basic U.S. Pat. No. 2,682,235. The traditional geodesic dome or structure comprises a grid of intersecting members which generally follow the lines of great circles or arcs of a sphere. Such lines are referred to as geodesic lines. The intersecting members form patterns of triangles which impart rigidity and structural integrity to the grid. The equilateral triangles of the pattern are congruent, or if different pattern triangles are incorporated in the grid, the number of different patterns is minimized. The conventional geodesic contruction uses the least number of repeated triangle shapes or patterns in order to minimize the mathematical complexity and consequent manufacturing complexity, retooling and expense.
The intersections where a plurality of struts or chords converge in a geodesic grid are referred to as vertices or nodes. According to conventional geodesic construction, the chords or struts are rigidly connected at the intersections. A variety of rigid hubs, joints, and connections have been used and are described in the literature. For example, fixed hubs for geodesic structures are shown in FIGS. 4 through 7 of U.S. Pat. No. 3,461,635. Rigid connecting devices for the vertices of spherical structures are also illustrated in U.S. Pat. No. 3,785,101, for example, FIG. 5. The Dome Builders Handbook in two editions published by Running Press, 38 South 19th Street, Philadelphia, PA 19103 describes a variety of rigid hubs and plates. Chapter 4 of the Geodesic Greenhouse published by Garden Way, Charlotte, VT 05445 is directed to rigid base hubs, pent hubs and hex hubs. Edmund Scientific of Barrington, N.J. offers the "Star Plate" rigid hub or joint for securing the vertices in geodesic structures, for example, "Star Plate", Serial No. K31,947 shown in the Edmund Scientific 1982 Fall Catalog.
The use of rigid hubs, joints and connections at the vertices or nodes of traditional geodesic structures is a consequence of the commitment to mathematical or geometrical regularity. The minimum number of equilateral triangle patterns, in turn minimizes the number of different central angles, axial angles and chord factors so that the same type of hubs may be repeated and fixed throughout the structure. Thus, the rigid hubs are particularly adapted to conventional construction methods where the same vertex configuration is repeated throughout the framework.
A disadvantage of the conventional methods, however, is that there is no flexibility in the structure particularly for closing or filling irregular spaces. The conventional method of construction is not well adapted to custom fitting and custom construction on site. There is no flexibility for adjusting the central converging angles of struts converging at a vertex of the grid, for adjustment of chordfactors to provide an irregular network of chords or struts in triangle patterns, and for adjustment of the depth of articulation of the struts at the vertices and the consequent dihedral angles of the triangle patterns relative each other. Furthermore, contrary to what might be initially assumed, the strict adherence to the pure mathematical and geometrical geodesic construction may be to the detriment of aesthetic considerations caused, for example, by the distortion or degradation of aesthetic lines.